The invention relates to a method for separating molecules having different excitation spectra and being components of a gas.
The invention further relates to a device for separating molecules having different excitation spectra and being components of a gas.
The invention further relates to a computer program for adjusting the laser pulses of a laser which is used to irradiate molecules of a gas in order to bring molecules to be separated into an excited state in which they can be extracted from the gas, and to a computer program product having such a computer program.
The molecules to be separated, which exist as parts of a gas, vary regarding their excitation spectra, i.e., regarding the position of the energy levels, which define the respective molecules' state of excitation. The term excitation spectrum is therefore used to describe the energetic state of a respective molecules' energy levels.
On one hand the molecules to be separated can be of different chemical properties, precisely, of a different chemical composition, thus different types of molecules which show different excitation spectra due to their different chemical properties. Or the molecules can be identical regarding their chemical properties and vary only in certain physical qualities, and therefore show different excitation spectra. The latter especially concerns isotopes of a particular molecular type, as the present invention also, predominantly concerns the matter of isotope separation (separation of molecular isotopes).
Here, the term molecules also refers to accumulations of atoms or molecules in the form of clusters, as described in Bergmann Schaefer, “Lehrbuch der Experimentalphysik”, band 5, Vielteilchen-Systeme, Walter de Gruyter Berlin 1992, chapter 8.
Various methods are known for separating molecules, which show different excitation spectra due to their isotopic composition. From the U.S. Pat. No. 5,827,405 a method is known for separating an isotope from a gaseous isotopic-mixture consisting of two isotopes. Thereby laser pluses are irradiated into the isotopic mixture, which non-selectively stimulate both isotopes into a higher electronic quantum state at first. The isotopes, whose excitation spectra are quite close within the energy spectrum, and don't overlap because of their only slightly varying masses, are thereby excited into quantized vibrational states. The isotopes' wave packets oscillate in phase at first, but diverge spatially because of their isotope specific progression.
In the method described in U.S. Pat. No. 5,827,405 the isotopes' electronic excitation energy is calculated as well as the time, after which the wave packets of the different isotopes have spatially diverged so far that they oscillate in anti-phase. At this moment an additional laser pulse is irradiated into the isotope mixture. The isotope to be separated is higher excited by absorption of a further energy quantum, without it being possible for the other isotope to absorb an energy quantum from the additional laser pulse, because the excitation spectra show different energy levels due to the spatial separation of the wave packets, thus the different distance of the isotope nuclei.
The multi-excited isotopes can then be extracted from the gas mixture by known methods. This can be induced for example by chemical reactions or by ionization of the isotopes using electro-static fields.
Another method described in U.S. Pat. No. 5,827,405 is the excitation of a second electron from its original ground state into the same quantum state as the first electron, using the second laser pulse. Thereby the moment of the second excitation is calculated in a way, that the second excited electron of the not to be separated isotope oscillates spatially with the first electron, but shifted in phase. As a result, the oscillatory states of the electrons mutually cancel each other out, and a third laser pulse further excites the electrons of the to be separated isotope; the isotope can then be extracted from the isotope mixture using the known methods.
It is a disadvantage of these two methods that the methods function only if the quantum states of the isotopes, as well as the time span in which the oscillating wave packets diverge, are precisely calculated beforehand.